Controlled photocycloaddition of stilbazolium ions intercalated in saponite clay layers

Abstract

The photochemical cycloaddition of stilbazolium ions intercalated in clay layers has been studied. syn Head-to-tail dimers were predominantly formed at the expense of E–Z isomerization which is a major path in homogeneous solution. The selective formation of head-to-tail dimers suggests that the intercalation occurs in an antiparallel fashion. The dimerization efficiencies were not affected even when the degree of adsorption of alkene molecules on the anionic-exchange site of the clay was decreased from 100 to 1%. The intercalated stilbazolium ions exhibited a strong excimer emission at 490–520 nm in addition to the monomer fluorescence at 380–450 nm. The strong excimer emission was not decreased even at 0.1% adsorption. These facts suggest that the intercalation starts via formation of small aggregates of adsorbate molecules, caused by their hydrophobic attraction. Details of the intercalation and photocycloaddition are discussed.